Impact of age at diagnosis of head and neck cancer on incidence of metachronous cancer

Metachronous cancer in patients with head and neck cancer (HNC) is common and is associated with a poor prognosis. We aimed to evaluate the incidence of metachronous cancer at different sites according to age at diagnosis of index HNC. We collected data on 2011 patients with oral cancer, oropharynx cancer, hypopharyngeal cancer, and laryngeal cancer as index cancers using the Osaka International Cancer Institute Cancer Registry database between 2005 and 2016. Among these, we analyzed 1953 patients after excluding 5 patients who were not followed-up and 53 patients with simultaneous multiple index cancers. We evaluated the cumulative incidence of metachronous cancer in the esophagus, lung, and other sites according to age at diagnosis of the index HNC using the Kaplan-Meier method. Multivariate logistic regression analysis was performed to identify factors that influenced the incidence of metachronous cancers following HNC. The cumulative incidence of metachronous esophageal cancer in young patients (